The purpose of this study is to increase our understanding of pressure disturbances in the eye by measuring the direct physical chemical interaction between blood and aqueous humor. The study will complement previous work on aqueous humor dynamics which has emphasized secretion and bulk outflow, and will provide a quantitative model for understanding pressure disturbances which occur in some clinically important ocular diseases. The method of the study is to use a living primate eye as the physiological model, under laboratory circumstances, in which many parameters of ocular fluid function can be monitored. Simultaneous measurement of intraocular pressure, venous pressure, arterial pressure, aqueous humor formation, and colloid osmotic pressure will allow calculation of the pressure insensitive secretory rate and the facility of colloid reabsorption of the whole eye using Barany's model. Measurements will be made in normal rhesus monkey eyes, in eyes in which retinal detachments have been produced by previous surgery, and in eyes in which corticosteroids have been administered chronically. Completion of Barany's model is hoped to improve our understanding of the secondary glaucomas and the secondary hypotonies and to suggest new therapeutic approaches to these disturbances. The relevance of these perfusion studies to clinical opthalmology will be augmented by a parallel study aimed at eliminating the systematic errors of tonography.